// 1像素边框
border-1px($color)
    position :relative
    &::after
        display: block
        position: absolute
        left: 0
        bottom: 0
        width: 100%
        border-bottom: 1px solid $color
        content: ' '
//去掉1像素
border-none()
    &::after
        display : none
//图标大小自适应
bg-image($url)
    background-image: url($url+"@2x.png")
    @media (-webkit-min-device-pixel-ratio: 3),(min-device-pixel-ratio: 3)
        background-image:url($url + "@3x.png")